Cure system for ethylene-vinyl chloride polymers



United States Patent 3,303,171 CURE SYSTEM FOR ETHYLENE-VINYL CHLORIDE POLYMERS Ann M. Schreiber, Parma Heights, Ohio, assignor to The triazines constitute the generic class of curing agents for combination with sulfur in this invention. These materials are represented by the formula "ice B. F. Goodrich Company, New York, N.Y., a corpora- 5 tion of New York N No Drawing. Filed June 1, 1965, Ser. No. 460,547

4 Claims. (Cl. 260--79.5) This invention relates to a process for the cure of NH rubbery ethylene-vinyl chloride copolymers. C

Copolymers of ethylene and vinyl chloride are old in i the art, being disclosed in United States Patent 2,200,429. Where R1, R2, and R3 are alkyl geeups containing from Processes for preparation of ethylene-vinyl chloride 1 to 4 carbon atoms and may all he the same, all he polymers are disclosed in United States Patents 2,342,400, ,difi t or he in any combination of C1 to 04 alkyl 2,388,178, 2,296,677, and 2,422,392. groups Ethylene-vinyl chloride copolymers containing from It is surprising that condensation .products of this 10% to 99% y Yvelght ethylene are fieXlble Plastlc or configuration serve very Well in combination with sulfur rubbery elastmgerlc m atena1S- These copolymers as curing agents for rubbery ethylene-vinyl chloride cop p l from 111eXPen$1Ve mnmeI5, ethylene Vlnyl polymers when somewhat structurally similar condensachlonde f are 9 great Interest to users of chlonnated tion products of aldehydes and amines and aldehydes and elastomeric materials for the manufacture of hose and aniline are f no value in this use. tubing, belts and film. Ethylene-vinyl chloride rubbers Rubbery ethylene-vinyl chloride copolymers are readily are saturated copolymers containing substantial amounts prepared by known bulk and emulsion polymerization of chlorine. They-are similar 11] structure to chlorinated systems Bulk polymerizatiohs are performed in high Polyethylene of 31mm chlorme oontentchlorobutyl pressure reactors at 1000 to 2000 atmospheres. Emulsion rubber and fhlorosulfonated Polyeflhylene are other polymerizati ons are run at 100 to 300 atmospheres. saturated, specialty rubber systems presently known and Polymers are purified by dissolving in solvent, clarifying, used. As With chlorobutyl rubber, and chlorosulfonated and reprecipitating. Compounding and mixing of the polyethylene, the uses to which the materials can be put polymers is Performed on standard rubber mixing equip will be greatly increased if a means can be found to cure ment, mills and the like or crosslink the polymers to give them increased strength, Stocks are preferably press cured, but hot oven or improved wear properties, and resistance to aging and autoclave curing is also f ibl weathering. The following example is set forth as illustrative of Aldehyde-ammonia condensation products and heptaldethis invention Parts are in Parts by weight hyde-aniline condensation products have been tried, both Example I alone and in combination with sulfur, without success in attempts to cure rubbery ethylene-vinyl chloride co- The P g Tempe 1s f i to a hlgh Pressre polymers polymerizer equipped for agitation and temperature con- When sulfur, the most widely known and used vultrol' canizing agent for rubbery materials, is used in curing 40 Part? by recipes with rubbery, saturated ethylene-vinyl chloride Matenfflz Welght copolymers the cure cannot be controlled and the stocks Vmyl chlonde 288 become degraded, blackened and brittle, with no favorable Etkylene 474 eiasto r p1'0pe1-fies Dnsopropylperoxy-dlcarbonat 0- *It has now been found that h bo t 1 to 3 parts The polymerization is run for 66 minutes at 50 C. of sulfur are combined with about 4 to 8 parts of Trimene and 27,000 P- with a Pressure drop of 6000 p Base per 100 parts copolymer in the cure of these ethylenethe P A White, elastomefic ethylene-Vinyl chloride vinyl chloride copolymers, rubbery, snappy materials usepolymer is purified by dissolving in chloroform and ful for extrusion and molding are produced. Furthermore reprecipita ing in methanol. The copolymer analyzes the ratio of Trimene Base to sulfur employed per 100 31.3% vinyl chloride and 68.7% ethylene by weight. parts of copolymer has been found to be critical in pro- DSV in cyclohexanone at 25 C. (0.4 g./100 ml.) is 0.890. ducing cured copolymer of the best stress-strain prop- The copolymer is compounded in the following recipes erties. The preferred ratio of Trimene Base to sulfur is on a laboratory mill by milling the stocks for about 15 from 2:1 to 4:1. Trimene Base is a commercial product, minutes. Data is set forth in Table 1. believed to be a condensation product of ethylene chloride, These vulcanizates of recipe D develop no cracks in formaldehyde and ammonia, and is further believed to a chamber ozone test of 335 hours. Oil and solvent have the configuration of 2,4,6-t1iethylheXahydro-S- resistance are excellent. Brittleness temperature is below i i 74 C. Pico Abrasion Index is 276 and the vulcanizates It is believed that alkyl substituted 2,4,6-heXahydro-S- are nonfiammable in ASTM test D-635-56T.

TABLE 1 Recipe A-BlClDEF Copolymer 100 100 100 100 100 100 Carbon black 40 40 40 40 40 40 Stearic acid- 1 1 1 1 1 1 Trimene Bas 3 1 3 5 3 5 Sulfur 0 2 2 2 0.5 0.5 Trimene Base/Sulfur ratio 3/0 0.5/1 1.5/1 2.5/1 /1 10/1 Min. cure at 310 F- 30 30 30 30 a0 30 Tensile (p.s.i.)- 1,270 1,100 2,140 3,760 2,450 1,780 Elongation (percent) 400 575 400 375 365 310 300% modulus 1,100 490 1,860 3,140 1,820 Remarks 1 Weak cure.

Iclaim: p 1. A vulcanizable ethylene-vinyl chloride copolymer composition comprising 100 parts of an unvulcanized ethylenevinyl chloride copolymer, about 1 to 3 parts of sulfur, and from about 4 to about 8 parts of an alkyl substituted 2,4,6-hexahydro-S-triazine of the formula wherein R R and R are alkyl groups containing from 1 to 4 carbon atoms, the ratio of said parts of triazine to said parts of sulfur being between 2:1 and 4: 1.

2. The composition of claim 1 wherein the 2,4,6- heXahydro-S-triaz'ine is 2,4,6-triethylhexahydro-S-triazine.

3. The process for curing ethylene-vinyl chloride copolymer compositions containing 10% to 99% ethylene by weight comprising adding to 100 parts of said copolymer from 1 to 3 parts of sulfur, and from about 4 to 4 about 8 par-ts ofan alky1 substituted 2,4,6-hexahydro-S- triazine of the formula References Cited by the Examiner V UNITED STATES PATENTS 1,989,042 1/ 1935 Kunz et a1 260.79'l 2,405,008 7/1946 Berry et a1. 260-79.5 2,416,878 3/1947 Lindsey et a1. 260-795 JOSEPH L. SCHOFER, Primary Examiner.

D. K. DENENBERG, Assistant Examiner. 

1. A VULCANIZABLE ETHYLENE-VINYL CHLORIDE COPOLYMER COMPOSITION COMPRISING 100 PARTS OF AN UNVULCANIZED ETHYLENEVINYL CHLORIDE COPOLYMER, ABOUT 1 TO 3 PARTS OF SULFUR, AND FROM ABOUT 4 TO ABOUT 8 PARTS OF AN ALKYL SUBSTITUTED 2,4,6-HEXAHYDRO-S-TRIAZINE OF THE FORMULA 